This disclosure is directed to a through tubing bridge plug adapted to set in a cased well even in the presence of formation fluids which might otherwise contaminate the cement plug supported by the bridge plug. For various reasons, it is often necessary to place a bridge plug in a completed well even though there may be production of formation fluids in the vicinity.
As an example, consider a well that is producing exoessive amounts of water from a depleted oil or gas zone. It may be beneficial to set a pIug above this depleted zone and produce from a more desirable upper zone. Assume also that the upper and lower zones may freely exchange fluids through perforations in the casing.
At this juncture, it is difficult to form a cured concrete plug with assurance of quality in view of the fact that the migrating fluids may contaminate the plug materials prior to setting and thereby damage the plug.
The present apparatus and procedure overcome this limitation. This enables a bridge plug to be set at a specified depth in a well notwithstanding the presence of migrating fluids in the well which might otherwise cause contamination. The present through tubing bridge plug can be anchored at a selected depth in a well and is held in position by expandable slips engaging the casing. The device has a petal basket which is deployed facing upwardly to receive sand and cement dumped by a bailer. There is a centrally located tubing which extends substantially well above the finished plug. Through a suitable valving arrangement (cooperative with fishing neck supported components) the plug is set in the casing while fluid is conducted through the through tubing. This bypasses the area where sand and cement is located. Thus, the through tubing and associated valving is selectively opened at the proper time, closed thereafter, and a fishing neck is retrieved to provide an indication external of the well that the valve closing sequence has been completed.
This arrangement thus enables the through tubing to divert fluid away from the uncured sand and cement. After curing, the bypass fluid can then be shut off by operation of the valve with a suitable overshot. This enables addition of sand and cement above the cured plug, thereby closing the well to additional flow permanently. When completed, the bridge plug is then underneath the concrete plug, the through tubing which was otherwise open is closed and covered over with the second pour which completes the concrete plug. Moreover, one of the components of the apparatus is selectively retrieved. Retrieval indicates proper setting and operation. Important additional features include an arrangement whereby torque applied to the bridge plug typically during makeup is not transmitted to the petal basket thereby avoiding twisting individual petal leaves. This prevents warpage of the petal basket upon deployment.